HGF and liver cancer: Until recently, the tumor formation risk due to MSCs has been assumed to be fairly low owing to their short life span in vivo with many studies suggesting that they have an inhibitory effect on tumor growth,35 such as in liver cancer caused by hepatocyte growth factor (HGF).36 This makes it all the more surprising that there is now a growing field of evidence which suggests that they have the ability to promote the growth of tumors.